fernando martínez-vidal, on behalf of the babar collaboration

Fernando Martínez-Vidal,On behalf of the BaBar Collaboration

Measurements of the CKM angle at BaBar

Fernando Martinez Vidal 1ICHEP 2010, Paris

• Apex of the CKM Unitary Triangle (UT) over constrained

• Precise measurement of SM parameters

• Search for NP in discrepancies of redundant measurements

• Still have some work to do on : less precisely known UT angle (most difficult to measure)

CP violation measurements give angles

Semileptonic decay rates (and other methods) give sides

Very impressive consistency

CKM angle

See also UTfit analysis athttp://www.utfit.org/

• Apex of the CKM Unitary Triangle (UT) over constrained

• Precise measurement of SM parameters

• Search for NP in discrepancies of redundant measurements

• Still have some work to do on : less precisely known UT angle (most difficult to measure)

CP violation measurements give angles

Semileptonic decay rates (and other methods) give sides

1

• Important to measure since, together with |Vub|, selects - value independently of most types of NP

SM candle type of measurement

• The constraint on come from tree-level B→DK decays

Fernando Martinez VidalICHEP 2010, Paris

Experiments providing most of analyses today

3.5 GeV e+ 8 GeV e–

657M BB pairs


468M BB pairs ~10-15o

Th

is t

alk

CKM angle

γ from B→DK decays

*

*

B

B

ICHEP 2010, ParisICHEP 2010, Paris

Measure interference between tree amplitudes b→u and b→c

• Use final state accessible from both D0 and D0

• Largely unaffected by New Physics

• Clear theoretical interpretation of observables in terms of γ

• Difficult because BFs are small due to CKM suppresion (10 -5-10-7, so not many events) and rB=|Aub|/|Acb| is small due to further CKM and color suppressions (small interference)

All measurements are statistics limited

Fernando Martinez Vidal 2

GLW

K- K+

π+ π-

K0s π0

K0s ω

K0s Φ

CP-e

ven

CP-o

dd

CP-conj CP-conj

K+π-

K+π-π0

K+π-π+ π-

ADS

K0s π+ π-

Dalitz plot

• Complementary methods applied on same B decay modes share the same hadronic parameters (rB, B) and

• Strategy: many decay chains are analyzed and then

combined to improve the overall sensitivity to γ

• In this talk we present new or recent results

Dalitz plot

π0 π+ π-

K0s K+ K-

CP-conj

K0s π+ π-

ADS

K+ π-

CP-conj

K+ π-π0

γ from B→DK decaysCharged B→D(*)0K(*) Neutral B→D(*)0K*0

rB~0.1 rB~0.3

K+ π- π+ π-

*

*

B

B

3ICHEP 2010, ParisICHEP 2010, ParisAtwood, Dunietz, Soni, PRL 78, 3357 (1997)

Gronau, London, Wyler, PLB 253, 483 (1991); PLB 265, 172 (1991)

f =

f =


)][( - BiiBS erKKBA

SKD0 SKD0

b→c b→u

)][( BiiBS erKKBA

SKD0 SKD0

b→c b→u

Hadronic parameters

D0 decay strong phase variation

Hadronic parameters

rB=|A(b→u)|/|A(b→c)|

B (strong phase difference between A(b→u) and A(b→c))

determined experimentally from data

Dalitz plot method


Decay amplitude

)(2 SKms

s

s

s

s

ss

ss

No D-mixing nor CPV

Bondar, unpublished.

Giri, Grossman, Soffer, Zupan, PRD 68, 054018 (2003);


)][( - BiiBS erKKBA

SKD0 SKD0

b→c b→u

)][( BiiBS erKKBA

SKD0 SKD0

b→c b→u

Relative weak phase changes sign

Decay amplitude


Interference terms in decay rates proportional to

Fit for x± and y± for each B decay mode

Dalitz plot method

No D-mixing nor CPV

)sin(

)cos(

BB

BB

ry

rx


)][( - BiiBS erKKBA

SKD0 SKD0

b→c b→u

)][( BiiBS erKKBA

SKD0 SKD0

b→c b→u

Decay amplitude


K 0sρK 0

sρ

K 0sρ

K 0sρ

No D-mixing nor CPV

Dalitz plot method

Large interference in some regions of the Dalitz plot, e.g.

D0→KS

D0→K*-+ vs D0→K*+-

DCS K*(892)+π-

CF K*(892)+π-

CF K*(892)+π- DCS K*(892)+π-

mES=√E*2beam -|pB*|2

jet-like

e+ e-

qqDπ sphericale+ e-BB

ΔE=EB*-E*

beam

• The main source of background : e+e- → qq, with q=u,d,s,c

• Event shape variables combined into a linear (Fisher) or non linear (Neural Network) combination. Tagging information sometimes used

mES

signal region

sidebands

Experimental techniques


• Signal is separated from background through unbinned maximum likelihood fits to B± → D(*) K(*)± data using mES, E and Fisher (or Neural Network) discriminant

• Use large B± → D(*) ± data control samples (rB~0.01, x10 smaller than for DK)

• Exclusive reconstruction of multiple B decays:

B±→DK±, B±→D* [D0]K± , B±→D* [D]K±, B±→DK*±

• Exploit kinematic constraints from beam energies.

ΔE

γ from D Dalitz plot method


• BaBar analysis based on complete data sample (468 M BB pairs)

• Reconstruct B±→DK±, B±→D* [D0]K± , B±→D* [D]K±, and B±→DK*± final states with D→KSπ+π-, KSK+K- (eight different final states for each B charge)

arXiv:1005.1096. Sub. to Phys. Rev. Lett.

B±→DK±Only BaBar

All componentsContinuum + BB BGContinuum + BB + D BG

• Efficiencies improved substantially (20% to 40% relative) with respect to previous BaBar measurement (383 M BB)

• Reprocessed data set with improved track reconstruction

• Improved particle identification

• Revised KS selection criteria: negligible background from D→+-h+h- and B→Da1(1260)

PRD78, 034023 (2008)

D→KS+-,KSK+K- amplitude analysis


• Extract D0 amplitude from an independent analysis of flavor tagged D0 mesons (D*+→D0π +)

• Experimental analysis using complete data sample benefits from synergy with D-mixing analysis

Model determined without (reference) and with D-mixing

• Fit for amplitudes relative to CP eigenstates [KS(770) and KSa0(980)] and assume no direct CPV

See Matt Bellis talk in this session for more details

ππ S-wave

Kπ S-wave

ππ P-wave

Kπ P-wave

ππ D-wave

Kπ D-wave

Wave ParameterizationK-matrix

K-matrix (LASS-like)

BW: ω(782), G.S ρ(770)

BW: CA and DCS K*(892), CA K*(1680)

BW f2(1270)0

BW CA and DCS K2*(1430)

K±Ks S-wave

K+K- S-wave

K+K- P-wave

K+K- D-wave

Wave Parameterization

BW: CA and DCS a0(980),

CA a0(1450)Flatte a0 (980), BW a0(1450) and f0(1370)

BW Φ(1020)

BW f2(1270)0

Main differences with Belle

Good fit quality (2/ndof) taking into account statistical, experimental and model uncertainties

arXiv:1004.5053. Accepted by Phys. Rev. Lett.



• CP violation parameters are extracted from simultaneous unbinned maximum likelihood fit to B± → D(*) K(*)± data using mES, E, Fisher and the Dalitz plot distributions (s+,s-)

B-→DK-

B+→DK+ B-→DK-

B+→DK+

B-→D*K-

B+→D*K+

B-→DK*-

B+→DK*+Differences between B+ and B- gives information on

B

10

)sin(

)cos(

BB

BB

ry

rx


γ from D Dalitz plot method• Use frequentist method to obtain the (common) weak phase and the hadronic parameters rB, B (different for each B decay channel) from 12 (x,y) observables

066.0062.0

*

042.0039.0

**

149.0)(

133.0)(

029.0096.0)(

DKr

KDr

DKr

S

B

B

)32111()(

)2182()(

)119()(

*

**

1920

DK

KD

DK

S

B

B

) 3 4 14 68 ()180 (mod stat syst

model

3.5 significance of CPV


• Smaller stat error due to additional data + improved reconstruction + slightly higher rB(DK)

• Model error benefited from overlap with D-mixing analysis (e.g. reduction of experimental uncertainties inherent to the model uncertainty)

) 5 5 22 76 ()180 (mod Our previous

result:

[Error on scales roughly as 1/rB]

) 8.9 3.6 78.4 ()180 (mod 8.10

6.11 040.0038.0160.0)(

DKrB


γ from ADS method


• Update with final data sample (468 M BB pairs). Previous analysis used 232 M BB pairs

• Reconstruct B±→DK±, B±→D* [D0]K± ,

and B±→D* [D]K±, with

• D→K±π- (“same sign”)

• D→K-± (“opposite sign”)

PRD72, 032004 (2005)

First sign of an ADS signal in B± → DK± (2.1)

and B± → D* K± (2.2)

B±→DK±

“Maximizes” CP asymmetry since “equalizes”the magnitudes of the interfering amplitudes

arXiv:1006.4241. Sub. to Phys. Rev. D

2.1

“op

po

sit

e s

ign

”

+

+

γ from ADS method


• Fit directly observables RADS and B± “same sign” yields to reconstruct the ADS asymmetry

cos)cos(2)(2

1 22DBDBDBADS rrrrRRR

ADSDBDBADS RrrRR

RRA /sin)sin(2

)][(

)][(

KKB

KKBR

D

D

)][( KKB D

008.0014.0013.0)]([

004.0009.0018.0)]([

002.0006.0011.0)(

*

0*

KDR

KDR

DKR

ADS

ADS

ADS

25.041.0

*

0*

12.016.0

94.036.0)]([

12.035.077.0)]([

47.086.0)(

KDA

KDA

DKA

ADS

ADS

ADS

B+→DK+ B-→DK-

Good sensitivity to rB


γ from ADS method


• Use frequentist interpretation (similar to Dalitz plot method) to obtain weak phase and hadronic parameters rB, B from RADS

(*) and AADS(*) observables

rD = (5.78 ± 0.08)% δD = (201.9 )ᵒ +11.4-12.4

(HFAG, CLEOc)

BaBar Dalitz plot method

|A(D0→ K-π+)|rD =

|A(D0→ K-π+)|

A(D0→ K-π+)δD = arg[ A(D0→ K-π+) ]

Inputs: (HFAG)

(CLEOc)

]83,54[ oo ]125.0,067.0[]175.0,094.0[


035.0051.0

**

051.0041.0

096.0)(

095.0)(

KDr

DKr

B

B

γ from GLW method


• Update with final data sample (468 M BB pairs). Previous analysis used 383 M BB pairs

• Reconstruct B±→DK± final states with D→K+K-,π+π- (CP even) and D→KS0,KS,KS(CP odd) (five different final states for each B charge)

• Efficiencies improved substantially (40% to 60% relative) with respect to previous measurement



• Introduce Fisher discriminant in the fit rather than apply cut on event shape variables

PRD77, 111102 (2008)

B-→DK- All componentsContinuum + BB BGContinuum + BB + D BG


γ from GLW method


• Extract signal yields fitting directly to observables R±K/ , RK/, and ACP±

)()(

)()(

KDBKDB

KDBKDBA

CPCP

CPCPCP

)()(

)()(/

CPCP

CPCPK DBDB

KDBKDBR

04.008.007.1

05.009.018.1

02.007.009.0

02.006.025.0

CP

CP

CP

CP

R

R

A

A

)()(

)()(00

00

/

DBDB

KDBKDBRK

3.6 significance of CPV in B±→DK± from ACP+


/

/

K

KCP R

RR

γ from GLW method



)()(

)()(

KDBKDB

KDBKDBA

CPCP

CPCPCP

)()(

)()(/

CPCP

CPCPK DBDB

KDBKDBR

04.008.007.1

05.009.018.1

02.007.009.0

02.006.025.0

CP

CP

CP

CP

R

R

A

A

)()(

)()(00

00

/

DBDB

KDBKDBRK



/

/

K

KCP R

RR

)1()1(4

1 CPCPCPCP ARARx

006.0007.0039.0060.0

007.0006.0037.0103.0

x

x

Consistent with and of similar precision to Dalitz results

[Dalitz results]

018.0042.0132.0

015.0039.0057.0

x

x

γ from GLW method



)()(

)()(

KDBKDB

KDBKDBA

CPCP

CPCPCP

)()(

)()(/

CPCP

CPCPK DBDB

KDBKDBR

04.008.007.1

05.009.018.1

02.007.009.0

02.006.025.0

CP

CP

CP

CP

R

R

A

A

)()(

)()(00

00

/

DBDB

KDBKDBRK



/

/

K

KCP R

RR

)1()1(4

1 CPCPCPCP ARARx

)(3.1 062.0189.0 GLW)(

)(3.0 055.0163.0Dalitz)(

xx

xx

Dalitz

γ from GLW method



)()(

)()(

KDBKDB

KDBKDBA

CPCP

CPCPCP

)()(

)()(/

CPCP

CPCPK DBDB

KDBKDBR

04.008.007.1

05.009.018.1

02.007.009.0

02.006.025.0

CP

CP

CP

CP

R

R

A

A

)()(

)()(00

00

/

DBDB

KDBKDBRK



/

/

K

KCP R

RR

)1()1(4

1 CPCPCPCP ARARx

040.0175.0 GLW)Dalitz( xx4.4 significance of CPV in B±→DK±

Dalitz+GLW

γ from GLW method


coscos21

sinsin22

BBB

BBCP rr

rA

Weak sensitivity to rB

• Use frequentist interpretation (similar to Dalitz plot method) to obtain weak phase and hadronic parameters rB, B from RCP± and ACP± observables

Fernando Martinez Vidal 17BaBar Dalitz plot

method

]83,54[ oo]125.0,067.0[

coscos21 2BBBCP rrR


Summary and outlook


• Recent progress on , the hardest UT angle to measure

• BaBar Dalitz plot method approach drives the measurement and benefited from synergy with D-mixing analysis (e.g. reduction of experimental uncertainties inherent to the model uncertainty) (see Matt Bellis talk later in this session)

• First sign of an ADS signal in B± → DK± and B± → D* K±

• Compelling evidence of direct CPV in B± → D(*)K(*)± decays

) 3 4 14 68 ()180 (mod stat syst

model

3.5 significance of CPV, B± → D(*)K(*)± combined, Dalitz only

18

3.6 significance of CPV, B± → DK± only, GLW only

Summary and outlook






18

4.4 significance of CPV in B±→DK±

only, Dalitz+GLW combined

040.0175.0 GLW)Dalitz( xx

Summary and outlook





Experiments providing most of analyses today

Experiments that can also give results in near future

Planned facilities


657M BB pairs


468M BB pairs ~10-15o

~2-3o

<1o • Need to reduce the error in order to see possible deviations

• Close to “last word” from BaBar (~10-15o error)

• Still statistics limited, even with full data sets

• BaBar “legacy” average from GLW, ADS and Dalitz plot methods in progress

Fernando Martinez VidalICHEP 2010, Paris 18

Backup

Instrumented Flux return

(Muon and hadron reco.)

Magnet(1.5 T)

Electromagnetic Calorimeter

(Detection of neutral particles)

Drift Chamber(Main tracking system)

Silicon Vertex Tracker(Tracking at low momentum and vertex reconstruction)

Detector of Internally Reflected Cherenkov(PID, Kaon separation

from pions)

• BaBar data taking ended on 7th April 2008

• BaBar recorded 470M BB at Υ(4S)

Delivered luminosityRecorded luminosity

Recorded Υ(4S): 432 fb-1

Recorded Υ(3S): 30.2 fb-1

Recorded Υ(2S): 14.5 fb-1

Off peak

Υ(4S)

Υ(3S)

Υ(2S)e-

e+

9GeV

3.1GeV

BaBar detector and data sample

γ from D Dalitz plot method• Signal yields as used in the final fit for CP parameters

• Efficiencies improved substantially (20% to 40% relative) with respect to previous BaBar measurement (383 M BB)



• Revised KS selection criteria: negligible background from D→+-h+h- and B→Da1(1260)

B decay mode BaBar (KS+-)468 M BB

BaBar (KSK+K-)468 M BB

Belle (KS+-)657 M BB

B±→DK± 896±35 154±14 757±30

B±→D*(D0)K± 255±21 56±11 168±15

B±→D*(D)K± 193±19 30±7 83±10

B±→DK*± 163±18 28±6 (not updated to 657 M BB)

PRD78, 034023 (2008)

PRD81, 112002 (2010) arXiv:1005.1096. Sub. to Phys. Rev. Lett.

D→KS+-,KSK+K- amplitude analysis

See Matt Bellis talk in this session for more details

540 800±800 79 900±300

• Extract D0 amplitude from an independent analysis of flavor tagged D0 mesons (D*+→D0π +)

• Experimental analysis using complete data sample benefits from synergy with D-mixing analysis

Model determined without (reference) and with D-mixing

• Fit for amplitudes relative to CP eigenstates [KS(770) and KSa0(980)] and assume no direct CPV

arXiv:1004.5053. Accepted by Phys. Rev. Lett.


ICHEP 2010, Paris

• CP violation parameters are extracted from simultaneous unbinned maximum likelihood fit to B± → D(*) K(*)± data using mES, E, Fisher and the Dalitz plot distributions (s+,s-)

B-→DK-

B+→DK+

Most precise measurement of (x,y)

Consistent results with latest Belle results

PRD81, 112002 (2010)


γ from D Dalitz plot method arXiv:1005.1096. Sub. to Phys. Rev. Lett.

Other hadronic parameters relevant for• Updated search for B+→D+K0 and B+→D+K*0

• Can only proceed through annihilation or rescattering

•Allows an estimation of rB0 for B0 from rB for B+ needed for

• B0→D0K0 measures rB0sin(2+) in time-dependent asymmetry

• B0→D0K*0 measures in direct CPV (similar to B+)

• BaBar analysis with full data sample: 468 M BB

• No evidence for signals

arXiv:1005.0068. Submitted to PRD

BaBar vs WA

) 73 ( 2416- ) 71 ( 21

25-

Courtesy of V. Tisserand and the CKM fitter group

Backup

CKM angle

)(

1)1(2

1

)(2

1

4

23

22

32

O

AiA

A

iA

Vij

d s bu t

c

Unitarity condition from 1st and 3rd columns

Wolfenstein parameterization

tcuui ,,

bsdd j ,,

• The electroweak coupling strength of W± to quarks described by the CKM matrix

Overconstraint apex coordinates

• CP violation measurements give angles• Semileptonic decay rates (and other methods) give sides• Precise measurement of SM parameters• Search for NP in discrepancies of redundant measurements

CKM angle


)][( - BiiBS erKKBA

SKD0 SKD0

b→c b→u

)][( BiiBS erKKBA

SKD0 SKD0

b→c b→u

Decay amplitude

K 0sρK 0

sρ

K 0sρ

K 0sρ

GLW

CP-even

CP-odd

π+ π-

K- K+

K0sπ0

K0sω

K0sρ

K0sΦ

GLW-like method

No D-mixing nor CPV

Strong phases varying over the Dalitz plane

Large interferences in some Dalitz plot regions

Gronau, London, Wyler, PLB 253, 483 (1991); PLB 265, 172 (1991)


)][( - BiiBS erKKBA

SKD0 SKD0

b→c b→u

)][( BiiBS erKKBA

SKD0 SKD0

b→c b→u

Decay amplitude

ADS

K+π-

K+π-π0

DCS K*(892)+π-

CF K*(892)+π-

ADS-like method

CF K*(892)+π- DCS K*(892)+π-

No D-mixing nor CPV

K+π-π+π-

Atwood, Dunietz, Soni, PRL 78, 3357 (1997)

Strong phases varying over the Dalitz plane

Large interferences in some Dalitz plot regions

fernando martínez-vidal, on behalf of the babar collaboration

Documents

e e qq

g strategy

babarfernando martinez

othis talkckm angle

anglessemileptonic decay

decay chains

known ut angle

b decay modes